Among the many insecticidal compounds, the phthalimidothiophosphates have reached a relatively high degree of commercial success. These compounds are toxic to a large number of insect pests at different concentrations varying with the resistance of the insects. Some of these compounds are described in U.S. Pat. No. 2,767,194, specifically N-(mercaptomethyl) phthalimide S-(O,O-dimethylphosphorodithioate).
The endeavor to extend the usefulness of the thiophosphates by increasing their effectiveness and lowering their cost has led to extensive studies on another class of biologically active chemicals, customarily referred to as activators. Among the many activators employed, the alkyl oxides, specifically piperonyl butoxide, have been widely used. These compounds are described in U.S. Pat. Nos. 2,485,681 and 2,550,737. In addition, vinyl thionophosphates containing an unsubstituted phenyl group have been found to be effective activators. These compounds are described in U.S. Pat. Nos. 3,380,887 and 3,886,273.